Tuning-Check
The report is written for people, not for programs. Every line says what has been changed and what that means for the vehicle.
A findings report, not a formal expert assessment. It records what is in the software and provides the evidence.
Contents
Rating
Not every change can be proven equally well. That is why every finding carries one of three ratings – so you know what you can rely on.
Limiters
This is what most people want to know first, and rightly so. More power on its own rarely causes damage. Damage happens when the limiters the manufacturer has set around the engine are missing.
Every engine control unit reduces power when things get too hot, the turbocharger spins too fast or combustion is no longer clean. That is deliberate.
Anyone who wants more power runs into exactly these limiters. So some raise them as well, switch them off or change the calculation they are based on. You notice none of this on the dyno or on a test drive. You notice it later: in the turbocharger, the pistons or the catalytic converter.
The list gives examples. We analyse all changes that the comparison with the original file shows – and, by arrangement, specifically the points you are interested in.
For each limiter, the report shows one of four results:
From the sample report
The calculation model for the exhaust gas temperature had been lowered by 5% across the entire range. As a result, the control unit calculated temperatures up to 64 K cooler than they actually were. At the same time, the threshold for enrichment had been lowered from 980 to 900 °C: enrichment therefore started slightly earlier, while everything else that depends on the calculated temperature saw exhaust gas that was too cool. You notice none of this while driving. To the sample report
Sample report
An extract from a real analysis, anonymised. A purchased tune for an Audi RS5, stated as 530 PS and 800 Nm.
The report is written so that you can understand it without prior knowledge: under every change it explains in plain language what it means and what consequences it can have.
Frankfurt (Oder)
Tuning-Check findings report
In short
Four limiters that, as standard, protect the engine, turbocharger and gearbox under high load and temperature have been changed: the exhaust gas temperature model is scaled to 95% across the entire range, and the control unit calculates up to 64 K below the factory calculation. At the same time, the threshold for enrichment has been lowered from 980 to 900 °C – enrichment therefore starts slightly earlier, while everything else that depends on the calculated exhaust gas temperature sees exhaust gas that is too cool. The charge reduction on pre-ignition is no longer active at 3,000 rpm and above. At normal air pressure, the turbo speed and pressure ratio limiter is slightly lower than the factory setting up to about 50 °C intake air, and higher above that and at altitude (up to +8%). The load axis of the torque calculation has been stretched from 230 to 270%: under high load, the control unit calculates torque up to 15% too low.
The extra power comes from three limiters together: the maximum torque including the stretched torque calculation, the air charge limiter (plateau raised from 215 to 260%, in all 5 copies) and the upper limit of the boost pressure (2.75 → 2.9 bar). In the log data, the air charge reaches up to 233.6%. The boost pressure target follows the higher air charge request; its maps are unchanged. At full load, enrichment starts earlier and is stronger, lambda down to 0.84. Driver demand, the gearbox message and the display are set at a constant 800 Nm, the maximum torque of the engine ECU at 760 Nm (internal torque). Calculated from the log data, the result is about 500 PS and about 750 Nm (factory 450 PS / 600 Nm); the control unit itself calculates at most about 660 Nm. The software does not reach the stated 530 PS and 800 Nm.
Seven fault codes for the exhaust system have been switched off. Whether the vehicle with this software is approved for use on public roads depends on the regulations of the country concerned and is decided by the authority responsible there; without the inspection required there, it is not automatically approved.
| Area | Factory | Now | Rating |
|---|---|---|---|
| Limiters against overload | |||
| Exhaust gas temperature, calculation model (675 cells) | factory values | all × 0.95, across the entire range – calculates up to 64 K too cool | confirmed |
|
What this meansThe engine control unit works out the exhaust gas temperature with a calculation, a so-called calculation model. This calculation was lowered by 5% across the entire range. As a result, the control unit calculates the exhaust gas up to 64 degrees cooler than the factory software does – in other words, cooler than it actually is according to the manufacturer’s calculation (calculated, not measured). Possible consequenceAt the same time, the threshold for enrichment has been lowered from 980 to 900 °C. As a result, enrichment at full load starts earlier and is stronger (down to lambda 0.84). Functions that only evaluate the calculated temperature react later. You notice none of this while driving. | |||
| Charge reduction on pre-ignition | active | no reduction at 3,000 rpm and above | confirmed |
|
What this meansUnder high load, the mixture in the cylinder can ignite by itself too early. This is called pre-ignition. From the factory, the control unit then reduces, among other things, the air charge – that is, air and therefore power. At 3,000 revolutions per minute and above, this no longer happens. Possible consequenceIf pre-ignition occurs in that range, the air charge stays high. Repeated pre-ignition can damage pistons, piston rings or connecting rods; the risk of this increases. | |||
| Turbo speed and pressure ratio limiter | dependent on air pressure and intake air temperature | at normal air pressure slightly lower up to about 50 °C, higher above that and at altitude (up to +8%) | confirmed |
|
What this meansThe engine has two turbochargers. The control unit limits how much boost pressure they may build up with two values: one for turbo speed, depending on air pressure, and one for the temperature at the compressor, depending on intake air temperature. Both have been changed: the turbo speed limiter has been lowered at normal air pressure and raised at altitude, and the limiter for warm intake air has been flattened. Together, at normal air pressure, the software allows 1 to 6% less than the factory setting up to about 50 °C intake air, and slightly more above that; at around 1,000 m altitude, up to 8% more. Possible consequenceAt higher altitude and with very warm intake air, the turbochargers may build up more pressure than the factory setting allows. This can shorten their service life. | |||
| Torque, calculation model | load axis up to 230% | stretched to 270% – calculates up to 15% too low | confirmed |
|
What this meansThe control unit calculates the engine’s torque from the air charge. The axis of this calculation has been stretched: at 230% air charge, the control unit now reads the value that belongs to 210% from the factory. Under high load, it therefore calculates up to 15% too low – in the log data at most about 660 Nm, whereas calculated from the air charge it is about 750 Nm. Possible consequenceEverything that depends on the calculated torque works with a value that is too small, including the torque limiters. Under high load, the control unit reports torque that is too low on the vehicle bus. Other control units, such as the gearbox and ESP, work with these values. | |||
| Power | |||
| Boost pressure target | unchanged | confirmed | |
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What this meansThe maps for the boost pressure target – the set value – were not changed. The target still rises, because the control unit calculates it from the requested air charge – and its upper limit has been raised (next row). Good to knowAn unchanged boost pressure target does not mean that the boost pressure stays the same. The boost pressure limiter is essentially unchanged from the factory: at 20 °C intake air and normal air pressure, 2.6 to 2.9 bar absolute instead of 2.75 bar. | |||
| Air charge limiter, 5 copies | plateau 215% | plateau 260%, reached in the log data: up to 233.6% | confirmed |
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What this meansThe air charge is the amount of air the cylinder may take in on each intake stroke. This is where part of the extra power comes from: the upper limit was raised from 215 to 260%. More air means more fuel and more power. The limiter appears in five places in the software. The 260% only applies with charge air up to 65 °C; at 80 °C it is 190 to 205% (factory 130 to 150%). In the log data, the air charge reaches up to 233.6%. Possible consequenceBoost pressure, temperatures and the load on engine, turbochargers and gearbox increase. That is part of any power increase. What matters is whether the limiters that cap it still take effect – here, four of them have been changed (see above). | |||
| Torque limiters (driver demand, gearbox, display) | speed-dependent | 800 Nm, flat across the rev range | confirmed |
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What this meansTorque is the turning force of the engine – put simply: how strongly it pulls. It is given in newton metres (Nm). From the factory, the permitted upper limit varies with engine speed. Now the same value applies everywhere: 800 Nm – for driver demand, for the message to the gearbox and for the display. The maximum torque of the engine ECU itself is set at 760 Nm (internal torque, before losses are deducted) from 2,500 to 6,000 rpm, slightly lower above that; from the factory it is 580 to 740 Nm depending on engine speed. Possible consequence800 Nm is an upper limit, not a measured value. It is not reached: calculated from the log data, it is about 750 Nm (see “Assessment”). The control unit itself calculates at most about 660 Nm, so the upper limit never takes effect in the log data (row “Torque, calculation model”). | |||
| Mixture at full load | lambda 1.0, with hot exhaust gas down to 0.88 | down to lambda 0.84 – enrichment earlier and stronger | confirmed |
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What this meansFrom the factory, lambda 1 is set at full load: exactly as much fuel as the air can burn. Extra fuel is only added once the calculated exhaust gas temperature reaches a limit value, and then down to lambda 0.88. Now this limit value is lower and the setting goes down to 0.84: in the log data, the mixture is enriched continuously from about 3,000 rpm. Possible consequenceThe additional fuel cools combustion and can thus offset some of the higher temperatures. In return, fuel consumption and emissions increase at full load. | |||
| Other changes | |||
| Display values | Stock | adapted to the new limiters | confirmed |
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What this meansValues that the vehicle displays or reports to other control units have been adapted to the new limiters. Possible consequenceThe display matches the new software. It is based on the control unit’s calculated values, and these are too low under high load (row “Torque, calculation model”). | |||
| Exhaust system fault codes | active | 7 switched off | confirmed |
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What this meansThe engine control unit monitors parts of the exhaust system, such as the catalytic converter and lambda sensors, and reports a fault there with a warning light and an entry in the fault memory. Seven of these fault codes have been switched off. The full report lists each one individually. Possible consequenceA fault in these areas is no longer reported, not even when the fault memory is read in the workshop. The report states what is in the ECU software. Whether a vehicle with this software is approved for use on public roads depends on the regulations of the country concerned and is decided by the authority responsible there. Modified engine or gearbox ECU software is not automatically approved without the inspection required there. | |||
Calculated from the ECU software
So the extra power comes from three limiters together – maximum torque including the stretched torque calculation, the air charge limiter and the upper limit of the boost pressure – not from the boost pressure target, which rises by itself with the air charge request. From the factory, it is usually the maximum torque that limits at full load, not the air charge limiter. How far the air charge actually rises in operation depends on boost pressure and charge air temperature. The log data show this.
Confirmed with the log data
The basis is four full-throttle accelerations in 5th gear. The air charge reaches at most 233.6%; the 260% is not fully used. In the mid-range, the control unit holds its calculated torque at about 660 Nm; above that, boost pressure is the limiting factor. These 660 Nm come from the gearbox ECU, which limits the reported torque. Because the torque calculation gives too low a figure, more is actually delivered: from the recorded air charge, calculated with the factory torque calculation, the result at the clutch is about 500 PS and about 750 Nm.
The stated 800 Nm appears as a constant value in the torque limiters. No engine has a maximum torque that stays the same across the entire rev range. The 800 Nm is an upper limit entered in the software; the engine does not reach it. The control unit itself calculates less, because its torque calculation has been changed.
Calculated from the ECU software and log data, at the clutch.
On the calculation: when developing our analysis system, we compared this result with a dyno measurement – the deviation was in the single-digit percentage range.
The full report lists every change individually: with address, stock value and new value – and with the same explanation in plain language.
Approach
We develop software ourselves. That is exactly why the report names no business and judges none. It describes the file: what has been changed, by how much and what follows from it.
What you do with the report is up to you. It is sent only to you.
On road approval: The report states what is in the ECU software. Whether a vehicle with this software is approved for use on public roads depends on the regulations of the country concerned and is decided by the authority responsible there. Modified engine or gearbox ECU software is not automatically approved without the inspection required there.
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